Create to place a back bet after certain amount traded

[buyshirts]

Hi
I want to offset a bet that has been placed into the market without any offset settings selected.
If for instance it is a large bet i would like it to offset the amount laid in small increments. I have been doing with the "Matched Bets Amounts condition" these works fine but i was wondering if i could use a signal and say for every £100 laid place a back.
Would i need to create a stored value to increase every time it's triggered?

Any help would be much appreciated.